Alarm systems



United States Patent ALARM SYSTEMS Robert J. Spooner, Essex, Conn.

ApplicationSeptember 24; 1954, Serial No. 458,140

4 Claims. (Cl. 340-213) This invention relates to an electric alarmsystem, particularly, of the type wherein an energized, normally closedsensing circuit is employed which when opened will effect the closing ofa signalor alarm circuit.

In general, the purpose of. this invention is to provide a system havingan alarm circuit that will be turned on remainon when activated by theopening of an energized, normally closed sensing circuit. This is ofparticular value in fire and burglar alarm installations. In such casesthe normally closed sensing circuit is equipped with devices that openthe circuit when an alarm is desired, and any opening of the sensingcircuit causes the alarm to operate. Once the alarm has started again,closing the circuit will not cut off the alarm.

One of the particular objects of the invention is to provide improvedenergizing sources for the sensing and alarm or signal circuits. Anotherobject of the invention is to provide relay means associated with thesensing and alarm circuits so arranged that when the sensing circuit isopen, the relay will be energized sufficiently to close the alarmcircuit and remain closed until the system is reset.

Further objects, details and advantages of my improved electric alarmsystem will appear in the following descriptinnof preferred embodimentsof my invention and illustrated in the accompanying drawings forming apart of this specification.

In the drawings:

Fig. 1 is a diagram illustrating an electric alarm circuit in accordancewith my invention;

Fig. 2 is a diagram illustrating a modification of the system shown inFig. l; and

Fig. 3 is a diagram illustrating a further adaptation of the system,wherein diiferent forms of independent electric energy sources areemployed for the sensing and alarm circuit of the system.

In general, the electric alarm system in accordance with my invention,includes a sensing circuit A and an alarm circuit B. In each instancethe external circuits are not shown, but are indicated by terminals aand a and b and b to which a normally closed sensing circuit external tothe system shown and an alarm device, such as a bell, siren, etc., arerespectively connected in the usual manner. These sensing and alarmcircuits each have its separate energizing supply or source C and D, Cand D and C and D in Fig. l, 2, and 3, respectively. Each adaptation isprovided with an on and off operating switch SW which may be used inconjunction with a pilot light for checking the external sensing circuitto see that it is in a normally closed condition. An alarm circuitswitch SW is provided to be closed after the sensing circuit is found tobe in its normally closed condition.

Each adaptation is further characterized by having a relay R which isenergized so as to attract an armature Ra, thereby displacing it fromits lower contact NC to its upper contact NO, when the external sensingcircuit is opened incident to operations of a burglar, fire or other2,814,795 Patented Nov. 26, 1957 circumstances to be indicated by analarm device, recorder or other appropriate device.

Each of these systems is primarily powered from the service mains ornetwork, customarily or volts A. 0, indicated at input. However, as willappear in connection with the adaptation Fig. 3 the entire system may beshifted for operation to a D. C. battery or direct current source D incase of power failure in the main or A. C. network.

Referring'particularly to Fig. 1, it will be seen that the A. C. sourceof the power input is connected through switch SW to the pilot lamp Land shunting resistance S and relay R in series. When switch SW isclosed, the current of said A. C. source passes through lamp L and itsshunt S as well as through the external sensing circuit which isconnected in shunt to the coil RC of the relay R, whereby a currentinsuflicient to operate this relay R to raise its armature Ra will flowthrough the relay coil RC. However, when the sensing circuit is opened,the current then flowing through this relay coil RC increasessuficient-ly to attract the armature Ra to break with its contact NC andmake with its contact NO. In this latter position, the full inputvoltage of the power source is applied to the alarm circuit connectedwith terminals b and b as long as both switches SW and SW remain closed.Under these conditions relay R remains energized and the alarm actuated,even though the sensing circuit may be closed again, for example, by aburglar noticing the alarm. To reset the alarm circuit, switch SW has tobe opened, whereby the relay R will be deenergized. Switch SW will alsobe opened, until the sensing circuit is checked by reenergizing it byclosing oi switch SW It will be seen that in this embodiment, the energyfor the sensing circuit is supplied through the lamp L and its shunt Swhich is sufficient for the purpose of energizing this sensing circuitacross the coil RC of the relay R. While the input is indicated as to beconnected directly across a, for example, 110 A. C. power source,obviously if the alarm system is to be operated on a lower voltage, theenergy may be derived from a battery or from a secondary of a step-downtransformer.

Such well-known step-down transformers are highly practical as source ofpower for my electric alarm system. The adaptation illustrated in Fig. 2is shown modified by employing two suitable step-down transformers C andD having their primaries connected in parallel across a 110 volt A. C.power source and their secondaries separately connected for energizingthe sensing and alarm circuits A and B, respectively. In thisarrangement it will be noted that these energy sources are separated incontrast to the arrangement of Fig. 1, where a single source is used.Yet, the operation of relay R is identical with that in the arrangementin Fig. 1. The two transformers C and D may be combined to a singlestructural unit.

In the modification shown in Fig. 3, instead of two transformersconnected in parallel with the input, the sensing circuit A is normallyenergized from a step-down transformer C when the latter is suppliedwith current via the A. C. input of, for example 110 volts, while thealarm circuit B is energized by an entirely distinct source of energy,i. e., a battery D of, for example, 8 volts. In case of power failure inthe A. C. supply, the sensing circuit is energized by a portion d forexample of 4 volts, of the battery D a tap d of this battery beingconnected by a conductor d to an upper contact r engaged by an armatureRa of a change-over relay R said armature being biased, for example by aspring (not shown) to assume this position when the relay coil RC is notenergized. In this condition, both the sensing and alarm circuits A andB are energized by the battery D or a portion thereof. This operation isimportant in the event of a failure of the A. C. current source, whichis mostly the general power network. It will be noted that in the normaloperation of the system, the A. C. current of the network is fed to thetransformer C thereby energizing the change-over relay R so that itsarmature Ra is attracted to engage a lower contact r and thereby connectthe secondary of the transformer C to the sensing circuit A. Thus thesensing circuit A is normally energized from the A. C. source throughthe transformer C and is energized by the battery current only in theevent of failure of the A. C. supply. The change-over relay R operatesautomatically, i. e. the change-over from transformer or A. C. supply tobattery and vice-versa takes place without manual actuation andinstantaneously.

The parts of the new electric alarm device or system, including relay orrelays, switches, pilot light, transformers and/ or battery, may bebuilt into or assembled in a common case to obtain a compact unit.

-It will be clear from the above description that many changes in thesystem or its circuits may be made without in any way departing from theessence of the invention as defined in the annexed claims.

I claim as my invention:

1. An electric alarm system including a normally closed sensing circuit,an alarm circuit, a source of electric energy for said sensing circuit,a source of electric energy for said alarm circuit, a pilot lamp in theconnections between said source of energy and said sensing circuit, aswitch for completing the circuit of said sensing circuit and said pilotlamp with its source of energy, whereby said pilot lamp will beenergized when said sensing circuit provides a closed circuit, a relayhaving an energizing coil connected in parallel with said sensingcircuit and normally substantially de-energized thereby, said relayhaving an armature carrying a movable contact element displaceabletogether with said armature from its normal position to an alarmposition when said relay coil is energized upon current increase due toopening of said sensing circuit, said relay being adapted to retain saidarmature in said alarm position upon opening of said sensing circuit,although the latter is subsequently reclosed, a first fixed contactopposite said movable contact to be engaged thereby when said armatureis displaced with said movable contact from said normal position to saidalarm position upon energization of said relay coil, said first fixedcontact and said movable contact being included in said alarm circuit, asecond fixed contact opposite said movable contact to be engaged therebywhen said armature is in said normal position while said relay coil isde-energized, said second fixed contact and said movable contact beingincluded in said sensing circuit, whereby upon energization of saidrelay coil incident to the opening of said sensing circuit and closingof said alarm circuit with its source of energy via said movable contactand said first fixed contact, said movable contact is separated fromsaid second fixed contact to open said sensing circuit which remainsinterrupted between said latter contacts, until said switch is openedcausing said relay upon de-energization of its coil to return itsarmature to its normal position.

2. An electric alarm system in accordance with claim 1, wherein saidsources of energy for said sensing and alarm circuits comprise a pair oftransformers having their primaries connected in parallel across anelectric energy source and having their secondaries separately connectedwith said sensing and alarm circuits.

3. An electric alarm system in accordance with claim 1, wherein saidsource of electric energy for said sensing circuit includes thesecondary of a transformer, the primary of which is connected with asource of electric energy and wherein said source of energy for saidalarm circuit comprises a direct current battery.

4. An electric alarm system in accordance with claim 3, wherein a relayis connected across said secondary of said transformer and is operableto connect said transformer secondary with said sensing circuit, whensaid transformer is energized, and when deenergized, the relay operatesto connect a portion at least of said alarmcircuit-energizing-batterywith said sensing circuit for energizing the same as long as saidcircuit remains closed.

References Cited in the file of this patent UNITED STATES PATENTS1,248,942 Sprague Dec. 4, 1917 2,621,240 Kemper Dec. 9, 1952

